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While Electricians were thus

most credit. contending, the ingenious I. A. De Luc proposed a system somewhat different from either of the former, an account of which may be found in his works, to which I refer the reader, and leave him to judge of the validity of it by the evidence there adduced. While some philosophers have contended for one fluid, and some for two, others have recently contended for no fluid at all, and have spoken of electrical effects as depending on the agencies of matter. Without dwelling on these adverse systems, which appear, in a great measure, verbal differences, I shall merely observe, tha+ there are certain modes of action of bodies on each other, such as all the phaenomena of artificial Electricity, &c. which custom has ascribed to the agency of a specific fluid. Whatever may be the principle of their action, the daily experience of philosophers shows the extent of this principle. Indeed, recent discoveries and experiments incline one to regard it as the universal agent in all the changes of form which matter undergoes.* A notion of the

* The discoveries made by Sir H. Davy seem calculated to throw light on this interesting subject.

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antiquity of which, though it be now newly revived as a subject of philosophical speculation, there appears some traces in the accounts left of the religion of Zoroaster, or the worship of the spirit of fire, as the soul of the universe, the source of all motion and of life.

In attributing the forms of Clouds, the production of Rain, and other atmospheric phaenomena, to Electricity, I would not be understood to involve any particular theory of the mode of electrical action. It is merely intended to ascribe similar appearances to similar causes, and to extend the principle of action upon which the phaenomena of artificial Electricity are explained, which has been identified with that of Lightning, to other atmospheric productions, which, at first sight, are less obviously referable to similar agencies.

I have already, in treating of M. Howard's theory of the modifications, shown how reconcileable that theory was to the various phaenomena exhibited by the clouds. There are many things, however, which I have not yet sufficiently explained, which may be mentioned in this place.

SECTION 1.

Of the Electric State of the Modifications of Clouds.

It is necessary to the present hypothesis, and is indeed conformable to constant experience, to consider Lightning, at least one kind of it, to be the discharge of the electric spark; and yet, at first view, the reconciling the electric charge of the nimbus, which would be necessary to the effect, with its being the result of the union of two dissimilarly electrified clouds, and consequent neutralization of the two Electricities, seems to involve a contradiction. To explain this, I must observe, that after two differently electrified clouds, whose structure and buoyance depended on the similar electric charge of their particles severally, have by a communication and the intense union of the said particles, formed the dense structure of the Raincloud, the latter cloud, when formed, may acquire a strong charge, for it would be thrown into an opposite state to that of the Earth, or other objects over which it might pass, or to other clouds in its vicinity; for its acquiring

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again a charge would not cause it to reassume the primitive structure of the clouds of which it was originally formed, for it now was condensed to minute drops of water, a state probably very different from that of any other modification. Under these circumstances, then, the Raincloud may exist as a highly electrified conductor: and it is probable that the difference between common Showers and Thunderstorms consists in the intensity of the charge which the nimbific mass may acquire after its formation.

It must be granted, that though the present theory seems so well to agree with the formation of Rain, it is nevertheless insufficient to account for all the varieties of the other modifications of clouds. We may readily conceive the fibrous structure, and other circumstances of the Curlcloud, to be the result of its office as a conducting body, effecting an electric communication; but we can assign no reason why a strong positive charge should produce a Sondercloud, instead of a collected mass like the Stackencloud, nor under what dissimilar circumstances Electricity should cause the infinite variety of forms under which these modifications, as well as the Curlcloud and

Wanecloud, appear on different occasions. It has been conjectured, that the plane Wanecloud is often placed between two differently electrified plates of air, between which it may be effecting a slow communication; and that the alternate bars of this cloud, at other times, may be interposed between portions of air alternately electrified with plus and minus. Experiments are wanting to ascertain these facts; but, could they be demonstrated, such an alternate distribution of the Electricity of the Air would remain unaccounted for. If the conjecture be true, the streaks of the Wanecloud may perform an office analogous to that of the water interposed between the plates of zinc and copper in the Voltaic Apparatus: and it is a fact, in some measure conformable to this idea, that this cloud, after losing its wavy or its striated appearances, has been observed to condense into a nimbus, and produce Rain without the help of any other cloud, as if it contained within itself the principles of its own resolution into water. The oblique and curved columns of the Wanecloud seem, indeed, hardly explainable even on this supposition. The curious cymoid feature, which so often precedes Storms, is not merely alternate bars, but the bars are

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